Work and Pensions Secretary Iain Duncan Smith is setting out his plan to encourage more people away from the benefits system and into work. But why has welfare reform so often proved so difficult?
It has become the Mission Impossible for successive governments. Changes to the benefits system have been repeatedly attempted and then abandoned or diluted.
So why this sorry saga of failure?
First, there is the sheer complexity involved in reforming such a labyrinthine system.
Department for Work and Pensions officials openly acknowledge they no longer know how many out-of-work benefits there are, and the government manual on benefits now runs to more than 10,000 pages.
Secondly, there is the habitual loss of political nerve, where governments faced by embarrassing demonstrations by disabled protesters invariably back off.
Labour's former welfare minister Frank Field recalls that when he threatened to go out and confront one such group of demonstrators, he was told by Downing Street to do no such thing. The result, he says was a government surrender over reform.
There has also been a pronounced lack of cross-party consensus over the issue, which has made pushing through difficult and controversial changes politically too painful.
And lastly, there has been a distinct lack of administrative continuity. In the last Labour government there were no fewer than eight different work and pensions secretaries in the past eight years.
Will this time be different?
Well, many of the previous difficulties no longer exist. There is more of a cross-party consensus and there is a political determination to push through the changes - but instead there are new obstacles.
Welfare reform in other countries has always been carried out in economic boom times.
Trying to get claimants back into work in an economic downturn when there simply aren't the same number of jobs available is much harder.
Introducing radical change has also always needed money up front to grease the wheels of reform and to help claimants back into work. Welfare reform is not cheap.
And yet public spending in Britain is being squeezed as never before with only £2bn set aside to bed in the government's planned changes.
At the same time those meant to be implementing the changes - DWP and Jobcentre staff - are facing a pronounced reduction in their numbers and resources.
None of which means welfare reform this time, like every other attempt, is doomed to fail. But the difficulties and political risks remain immense.